A UK-based
company is now offering a range of temperature limiters/controllers,
pressure transmitters, screw-in transmitters, submersible probes
and level control switches, all with SIL2 (Safety Integrity Level
2) approval for hazardous environments.

The new range, supplied by Impress Sensors & Systems, a specialist
manufacturer and distributor of sensors, instrumentation and
complete system packages, based in Aldermaston, Berkshire 
is targeted at safety and hazardous area applications, including
process manufacturers, chemicals, oil and gas, nuclear and Atomic
Weapons establishments. The devices are also suitable for medical
device applications.

The process industry demands the highest degree of safety and
reliability these days. The current Safety Integrity Level (SIL)
international safety standard provides suppliers and users with
a common framework on which to design products and systems for
safety related applications. The standard also provides a more
scientific, numerical approach to specifying and designing safety
systems, enabling the nature of the risk to be quantified.

SIL means risk reduction to a tolerable level. The required safety
level of a process plant is classified in accordance with the
international IEC 61 511 standard and depends on the risk constituted
by a plant. The IEC 61 508 standard describes the requirements
of electrical, electronic and programmable electronic devices
used in such plants. Both standards subdivide plants and devices
into 4 safety levels, from SIL1 for low risks, to SIL4 for very
high risks. The allocation to these safety levels is based on
the use of a risk graph and depends on:

The standards also describe the type of risk assessment and procedures
for integrating certain safety functions into sensors and plants.
Generally, the significant hazards for equipment and any associated
control system have to be identified by the specifiers or developers
via a hazard analysis. The analysis identifies whether functional
safety is necessary to ensure adequate protection against each
significant hazard.

For more information on Impress Sensors range of SIL2-certified
pressure, temperature and level control switches, contact the
sales department at Impress Sensors & Systems Ltd on 0118
981 7980 or visit the website at www.impress-sensors.co.uk
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